Cook rice and keep warm. Warm flour tortillas and keep covered. Slice onion and peppers into strips. Mix fajita seasoning in a small bowl.
Boil frozen corn on the cob in lightly salted water until tender. Drain and set aside.
Season chicken thighs with lime juice and fajita seasoning. Toss onion and peppers with a little oil, salt, and the same seasoning mix.
Preheat griddle to medium-high heat. Sear chicken thighs until golden on both sides and fully cooked. Move to cooler side of the griddle to rest.
Add onion and peppers to the hot side of the griddle. Cook until softened with light char. Place corn on the griddle (or grill outdoors) and cook until charred on all sides. Slice kernels from the cob.
Slice chicken. Build bowls with rice, chicken, onions, peppers, corn, cheese, and cilantro. Serve with tortillas and adobo ranch on the side.